<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        let arrAges = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
        let sum = 0
        let average
        for (i = 0; i < arrAges.length; i++) {
            sum += arrAges[i]
            average = sum / arrAges.length
        }
        document.write(`平均年龄是${average}`)
    </script>
</body>

</html>